With the development of industry, pumps have been widely used in various power machinery as a power source for liquid flow in mechanical systems. For an internal combustion engine, the fuel system, lubricating system and cooling system all require a pump to drive liquid in these systems to achieve liquid circulation in the systems. With respect to the cooling system, a coolant pump drives a coolant, which makes the coolant flow over cylinders of the internal combustion engine to take away heat generated by the internal combustion engine. As such, the internal combustion engine would not be overheated.
There typically has two kinds of pumps, i.e., mechanical pumps and electric pumps. A mechanical pump is usually driven by the internal combustion engine of a vehicle, where power of an output shaft of the internal combustion engine is transmitted to the pump through belts, which is simple in construction. In this case, the rotation of the mechanical coolant pump is decided by the engine and can hardly be adjusted by a user. An electric pump is powered by electricity and controlled by an independent electrical control unit. In this case, the electric pump is not subject to the rotation speed of the engine, and the output power of the coolant pump can be adjusted according to various temperature of the internal combustion engine. The electric pump can operate flexibly and is more energy-efficient.
A conventional electric coolant pump typically includes a motor and an impeller driven by the motor. The motor includes a stator and a rotor rotatable relative to the stator. The stator is wound with windings which are connected to the electrical control unit. The rotor is provided with a magnet. The impeller is connected to the output shaft of the rotor. The electrical control unit controls the intensity and direction of the electrical current flowing through the stator windings, making the stator windings generate a variable magnetic field. The variable magnetic field interacts with the magnet of the rotor to drive the rotor and hence the impeller connected to the rotor to rotate, which in turn drives the coolant to circulate in the cooling system loop and cool the vehicle internal combustion engine to avoid be over-heated.
Because the electric cooling pump is electrically controlled, the electrical control unit itself generates a large amount of heat during operation of the pump. If the heat cannot be effectively dissipated and therefore accumulated within the coolant pump, the electrical control unit may work at a high temperature state, which may cause failure of the electrical components and affect the reliability of the coolant pump. The electric coolant pump usually includes a housing and a cover. In assembly, the housing and cover need to be sealed to avoid liquid leakage. In addition, assembly of the housing and the cover follows strict procedures, which limits the production efficiency.